High latent air handling unit

ABSTRACT

An air handling unit (AHU) comprises a shell defining a cavity and comprising at least an air ingress on a shell surface and an air egress on another shell surface, a condensing coil disposed with the cavity, a cooling coil disposed between the air ingress and the condensing coil, and an energy recovery coil disposed between the condensing coil and the air egress.

BACKGROUND OF THE INVENTION

Indoor facilities can require meticulous control of various environmental conditions, which can be dependent upon the use and function of the corresponding indoor facilities. For example, indoor office spaces may require low temperature and low humidity in order to keep personnel comfortable during the work day. The heat required to increase or decrease the temperature of the air without changing the quantity of water vapor in the air is classified as “sensible” heat. Heat required to increase or decrease the quantity of water vapor without changing the temperature is considered “latent” heat. Conventional air handling units (AHUs) are typically designed to control temperature such that latent-to-total heat regulation is less than 50%.

Some environments, however, may require higher latent-to-total heat regulation. For example, natatoriums, laboratories that utilize once-through air, high-occupancy areas including indoor sports and concert venues, commercial and industrial kitchens, wash areas, greenhouses and indoor grow spaces may benefit from having a higher latent-to-total heat regulation, which provides for greater control of the humidity of the environment.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and desired objects of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawing figures wherein like reference characters denote corresponding parts throughout the several views.

FIG. 1 depicts a psychrometric chart for air handling units (AHUs).

FIG. 2 depicts a high latent AHU (HLAHU) according to an embodiment of the claimed invention.

FIG. 3 depicts a workflow process for regulating temperature according to an embodiment of the claimed invention.

DEFINITIONS

The instant invention is most clearly understood with reference to the following definitions.

As used herein, the singular form “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from context, all numerical values provided herein are modified by the term about.

As used in the specification and claims, the terms “comprises,” “comprising,” “containing,” “having,” and the like can have the meaning ascribed to them in U.S. patent law and can mean “includes,” “including,” and the like.

Unless specifically stated or obvious from context, the term “or,” as used herein, is understood to be inclusive.

Ranges provided herein are understood to be shorthand for all of the values within the range. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or sub-range from the group consisting 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 (as well as fractions thereof unless the context clearly dictates otherwise).

DETAILED DESCRIPTION OF THE INVENTION

Described herein are systems and methods for regulating air temperature. A high latency air handling unit (HLAHU) can be an AHU that regulates a temperature via a high latent-to-total heat. The HLAHU can include multiple coils disposed within a unit shell. The multiple coils can include a cooling coil, a condensing coil, and an energy recovery coil. The coils can flow a fluid throughout, which can alter the temperature of, and water vapor contained within, air passing through the HLAHU. The HLAHU can regulate temperature of an environment with a high latent-to-total heat, such as 80% latent-to-total heat.

In many cases the function of a facility is considered optimum when air temperature and humidity are kept within a very narrow range. The maximum amount of water vapor in the air is directly dependent upon the temperature of the air. Higher temperature air can hold more water vapor that lower temperature air. Increasing or decreasing the temperature of the air without changing the quantity of water vapor in the air is classified as increasing or decreasing “sensible” heat. Increasing or decreasing the quantity of water vapor without changing the temperature is considered increasing or decreasing “latent” heat.

FIG. 1 depicts a psychrometric chart for AHUs. For a typical AHU, the ratio of latent to total heat is typically less than 50% and frequently less than 40%. This psychrometric chart depicts separated sensible and latent heat regulation for a single condensing coil of an AHU. As an example of a conventional AHU, latent heat can account for approximately 45% of the total heat required to remove the desired quantity of water vapor.

Using the HLAHU in lieu of a conventional cooling coil, the latent load can be, for example, 72% of the total heat required to remove the desired quantity of water vapor. This can represent a 37% reduction in cooling energy to remove the same quantity of water vapor and a 68% reduction in the sensible heat load.

FIG. 2 depicts a HLAHU according to an embodiment of the claimed invention. The HLAHU can include an exterior shell 205 for containing the various other components of the HLAHU. While FIG. 2 depicts a rectangular shell 205, one skilled in the art will appreciate that the shell can be any number of shapes and sizes, and composed of various materials, while still maintaining the purpose of containing the various other components as described more fully herein.

The exterior shell 205 can include an ingress 210 and egress 215. The ingress 210 and egress can be openings on the exterior shell 205 that allow for ambient air to enter and exit, respectively, the exterior shell 205. The ingress 210 can be located on a different surface or side of the exterior shell 205 compared to the egress 215. For example, the ingress 210 can be located on a side of the exterior shell 205 opposite of a side of the shell 205 the egress 215 is located on. This may provide a benefit of allowing air entering the HLAHU to flow through the length of the HLAHU prior to exiting via the egress 215. Each of the ingress 210 and egress 215 can include one or more holes, slots, perforations, apertures, orifices, and the like.

The HLAHU can further include a cooling coil 220 located within the exterior shell 205. The cooling coil 220 can include a series of fluidic channels that form a number of windings along the length or width of the cavity formed by the exterior shell 205 (e.g., so as to span a dimension of the cavity). The cooling coil can further include thermally conductive material, such as aluminum, tungsten, nickel, silver, zinc, graphite, silicon carbide, copper, stainless steel, and the like. A fluid can be flowed through the cooling coil 220. A difference in the temperature of the fluid in the cooling coil 220 and the temperature of the air passing over the cooling coil 220 can cause a thermal transfer between the air and the cooling coil 220 (e.g., between the air passing over the coil, the coil material, and the flowing fluid). The fluid can include compositions such as water, Freon, other industrial refrigerants, and the like. Further, in some examples, the cooling coil 220 can be microchannels, which can include a set of coil windings with surface area-to-volume substantially greater than conventional cooling coil piping. Higher surface area-to-volume ratios can result in higher heat transfer and greater effectiveness of the invention described herein. Due to the smaller diameter, microchannels can provide larger surface area exposed to passing air, which can generate a larger thermal transfer rate between the air and the cooling coil 220.

The HLAHU can also include a condensing coil 225. The condensing coil 225 can be disposed within the cavity formed by the exterior shell 205. Further, the condensing coil 225 can be located between cooling coil 220 and the egress 215, such that air entering the cavity flows past the cooling coil 220 prior to passing over the condensing coil 225. The condensing coil 225 can span the same dimension of the outer shell 205 as the cooling coil 220 (e.g., the width of the exterior shell 205, the length of the exterior shell 205, and the like). The condensing coil 225 can include a series of fluidic channels further composing a series of windings. Further, the condensing coil can include thermally conductive material, such as copper tubing with aluminum fins. As air within the HLAHU passes over the condensing coil 225, water vapor held within the air can condense (e.g., due to the temperature difference between the fluid entering the condensing coil 225 and the air) and deposit onto the condensing coil 225. The temperature difference between the fluid entering the condensing coil 225 and the air passing over the coil 225 can also cause thermal transfer to occur, where thermal energy can be passed between the air, the condensing coil 225, and the fluid flowing in the coil 225.

The HLAHU can also include an energy recovery coil 230. The energy recovery coil 230 can also be disposed within the cavity of the exterior shell 205. The energy recovery coil 230 can be located between the condensing coil 225 and the egress 210, such that air entering the cavity passes over the condensing coil 225 prior to passing over the energy recovery coil 230. The energy recovery coil 230 can span the same dimension of the outer shell 205 as the cooling coil 220 and the condensing coil 225 (e.g., the width of the exterior shell 205, the length of the exterior shell 205, and the like). The energy recovery coil 230 can include a series of fluidic channels that form a number of windings along the length or width of the cavity. The energy recovery coil 230 can further include thermally conductive material, such as aluminum, tungsten, nickel, silver, zinc, graphite, silicon carbide, copper, stainless steel, and the like. In some examples, the energy recovery coil 230 can include microchannels. The energy recovery coil can further regulate the temperature of the passing air, while also regulating the flowing coolant prior to the coolant reentering a coolant supply basin. This can reduce the energy required to regulate the coolant within the supply basin, which can reduce associated costs and energy expenditure for the HLAHU.

Coolant Flow Path

The coolant within the cooling coil, condensing coil, and energy recovery coil can flow in a predefined order between the corresponding coils. For example, the coolant may originate in a coolant supply basin (not shown), which may be within the cavity or external to the cavity of the exterior shell. The coolant can be conditioned within the supply basin, for example chilled or heated to a desired temperature. The coolant can then be pumped (e.g., via a fluid pump) through the condensing coil. An end of the condensing coil can be coupled to the supply basin, and another end of the condensing coil can be coupled an end of the cooling coil. Another end of the cooling coil can be coupled to an end of the energy recovery coil. Another end of the energy recovery coil can be coupled to the supply basin. Thus, a fluid loop can be created between the supply basin, the condensing coil, the cooling coil, and the energy recovery coil with the fluid originating and returning to the supply basin.

The HLAHU can also include a split-flow device, such as a flow limiter. The split-flow device can be coupled to the condensing coil, the cooling coil, or both. The split-flow device can redirect a portion of the coolant flow from the condensing coil back to the supply basin, as opposed to entering the cooling coil. In some cases, the split flow device can be configurable, so that the fluid flow into the cooling coil is regulated, for example in order to maximize energy efficiency.

A table of example air temperatures passing through or across the different components of the HLAHU (e.g., a 4,000 CFM unit) is provided below:

Entering Air Leaving Air Temperature Temperature Cooling Coil 78.0° F. 61.0° F. Condensing Coil 61.0° F. 43.9° F. Energy Recovery Coil 43.9° F. 67.0° F. Reheat Coil 69.0° F. 86.0° F.

The table above illustrates the effect the respective coils have on air passing through the HLAHU. As discussed above, the reheat coil can be optional (or optionally activated), for example in cases where the temperature of exiting air from the energy recovery coil of the HLAHU is desired to be higher than the air entering the HLAHU.

A table of example coolant temperatures flowing through the different components of the HLAHU is provided below:

Entering Coolant Leaving Coolant Temperature Temperature Condensing Coil 42.0° F. 57.0° F. Cooling Coil 57.0° F. 73.6° F. Energy Recovery Coil 73.6° F. 49.4° F. Reheat Coil 117.0° F.  100.0° F. 

The table above illustrates the thermal energy transfer to the coolant flowing the respective coils caused by the air passing through the HLAHU. The above table also provides an illustration of coolant flow throughout the entire HLAHU: through the condensing coil, to and through the cooling coil, and to and through the energy recovery coil. As stated previously, the reheat coil may be a separate component apart from the other coils, and may receive and return heating fluid to a supply basin apart from the other coils, or in some cases may include its own separate supply basin.

A table of example coolant flow rates flowing through the different components of the HLAHU is provided below:

Gallons per minute Cooling Coil 8.7 Condensing Coil 22.6 Energy Recovery Coil 8.7 Reheat Coil 10

As shown in the table above, a portion of the coolant from the condensing coil can pass to the cooling coil, and subsequently to the energy recovery coil. This can be caused, and regulated by the split flow device described above. The remaining coolant not passing to the cooling coil can return back to the supply basin.

Benefits

The HLAHU described herein can provide for a multitude of benefits. For example, heat transfer devices of the microchannels or similar design of the cooling coil and/or energy recovery coil can generate closer approach temperatures and higher efficiencies. The split-flow device can generate energy recovery (e.g., from coolant returning to the supply basin). The once-through flow of coolant from the condenser coil to the cooling coil and the energy recovery coil, and back to the coolant return, can represent significant improvements over less-efficient runaround coil technologies. The HLAHU described herein can also reduce flow of central plant cooling, and can operate with or without the addition of outside air or exhaust. The improved efficiency of the HLAHU allows for the use of a wider range of coolant types within the system.

Workflow Process

FIG. 3 depicts a process flow for regulating temperature according to an embodiment of the claimed invention. The process flow can be performed by an AHU (e.g., a HLAHU) as described with reference to FIGS. 1 and 2 above.

At Step 305, an AHU can flow a volume of air across a cooling coil. Flowing the volume of air across the cooling coil decreases a temperature of the volume of air. In some cases, the temperature of the volume of air subsequent to the flowing across the cooling coil is at a dew point relative to the temperature of the volume of air prior to flowing across the cooling coil. In some cases, the temperature of the coolant flowing through the cooling coil can increase to a temperature approximating the temperature of the air entering the cooling coil.

At Step 310, the AHU can flow the volume of air across a condensing coil. Flowing the volume of air across the condensing coil decreases the temperature of the volume of air. In some cases, flowing the volume of air across the condensing coil decreases a mass of water vapor contained in the volume of air.

At Step 315, the AHU can flow the volume of air across an energy recovery coil. Flowing the volume of air across the energy recovery coil increases the temperature of the volume of air. In some cases, the temperature of the air leaving the energy recovery coil can approximate the temperature of the coolant entering the energy recovery coil. At Step 320, the volume of air can exit the AHU.

EQUIVALENTS

Although preferred embodiments of the invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

INCORPORATION BY REFERENCE

The entire contents of all patents, published patent applications, and other references cited herein are hereby expressly incorporated herein in their entireties by reference. 

1. An air handling unit (AHU), comprising: a shell defining a cavity and comprising at least an air ingress on a shell surface and an air egress on another shell surface; a condensing coil disposed within the cavity; a cooling coil disposed between the air ingress and the condensing coil; and an energy recovery coil disposed between the condensing coil and the air egress.
 2. The AHU of claim 1, wherein the condensing coil is in fluidic communication with the cooling coil.
 3. The AHU of claim 2, further comprising a fluid flow rate limiter configured to limit fluid flow from the condensing coil to the cooling coil.
 4. The AHU of claim 1, wherein the cooling coil is in fluidic communication with the energy recovery coil.
 5. The AHU of claim 1, further comprising: a coolant return basin in fluidic communication with the condenser coil and the energy recovery coil, wherein the coolant return basin is configured to receive fluid flow from the energy recovery coil and excess fluid flow from the condenser coil.
 6. The AHU of claim 1, further comprising a fluid pump configured to flow fluid, in order, through the condenser coil, to and through the cooling coil, and to and through the energy recovery coil.
 7. The AHU of claim 1, further comprising a motorized fan disposed within the cavity, the motorized fan configured to flow air, in order, through the air ingress, across the cooling coil, across the condensing coil, across the energy recovery coil, and through the air egress.
 8. The AHU of claim 1, wherein the cooling coil, the energy recovery coil, or both, comprise a set of fluidic microchannels.
 9. The AHU of claim 1, wherein the condensing coil comprises copper tubing with aluminum fins.
 10. The AHU of claim 1, further comprising a fluid reheating coil disposed between the energy recovery coil and the air egress.
 11. A method for regulating temperature, comprising: flowing a volume of air across a cooling coil of an air handling unit (AHU); flowing the volume of air across a condensing coil of the AHU; flowing the volume of air across an energy recovery coil of the AHU; and exiting the volume of air from the AHU.
 12. The method of claim 11, further comprising: flowing the volume of air across a fluid reheat coil subsequent to flowing the volume of air across the energy recovery coil.
 13. The method of claim 11, wherein flowing the volume of air across the cooling coil decreases a temperature of the volume of air.
 14. The method of claim 13, wherein the temperature of the volume of air subsequent to the flowing across the cooling coil is at a dew point relative to the temperature of the volume of air prior to flowing across the cooling coil.
 15. The method of claim 11, wherein flowing the volume of air across the condensing coil decreases the temperature of the volume of air.
 16. The method of claim 11, wherein flowing the volume of air across the condensing coil decreases a volume of water vapor contained in the volume of air.
 17. The method of claim 11, wherein flowing the volume of air across the energy recovery coil increases the temperature of the volume of air. 